1. Field of the Invention
The present invention relates to antennas and, more particularly, to a planar bilayer microstrip reflector antenna that increases the antenna gain-bandwidth.
2. Description of Related Art
In comparison with parabolic reflector antennas, micros trip reflector antennas employ relatively new technology. A parabolic reflector antenna has a curved surface. A microstrip reflector antenna can be made having a planar surface. Further, a microstrip reflector antenna can achieve the concentration of antenna beam in a particular direction by means of the application of one of several methods.
However, conventional microstrip reflector antennas that achieve concentration of antenna beam by different methods have the common problem of narrow gain-bandwidth. Methods of improving the problem of narrow gain-bandwidth are reported in specific issues. However, these reports are commonly of a single layer design formed of a single printed circuit board (see FIG. 7). Taiwan Patent Publication No. 242711 discloses a single dielectric layer microstrip reflector antenna. Improving the bandwidth of this design of single dielectric layer microstrip reflector antenna can be achieved only by increasing the thickness of the dielectric layer. −3 dB gain-bandwidth can be achieved to 7.2% for this design of antenna. Increasing the thickness of the dielectric layer may cause the so-called surface wave phenomenon, thereby reducing antenna efficiency accompanying with the problem of high radiation level from delay circuit.
Therefore, it is desirable to provide a bilayer microstrip reflector antenna that eliminates the aforesaid drawbacks.